1. Field of the Invention
This invention relates to medical instruments. It applies to medical needles in general and specifically to the needles used for placing an intravenous catheter into a vein, although it can also be applied to other hypodermic needles. In the U.S. Patent Office it would be found in a classification for needle tip guards which protect health care workers from accidental needle sticks.
2. Description of the Prior Art
At this time the need for needle guards which protect health care workers from exposure to AIDS and hepatitis and the like through accidental needle sticks has been well established. A multitude of these protection devices exist in the prior art and some have made their way to the market place.
Many of the devices of the prior art apply specifically to intravenous catheter insertion kits. Such a kit is generally comprised at least in part of an insertion needle inside a flexible catheter which in turn is attached to a standard fluid fitting, usually referred to as a hub. In operation the insertion needle and surrounding catheter together enter the patient's vein. The needle is then removed leaving the catheter in place inside the vein. Fluid lines for administering medications or nutrients can then be attached to the hub through a standard Luer lock or other convenient means and the fluids can then be fed though the catheter directly into the blood vessel.
The problem the devices of the prior art attempt to solve is how to protect health care workers from the sharp point of the insertion needle which has been exposed to possibly contaminated blood. This applies to personnel who must dispose of the needle as well as those who must manipulate the needle at withdrawal, and is of special concern during emergency situations when care must be administered quickly to patients of unknown health status using possibly inadequate disposal facilities. For example, many I.V.s must be administered at the site of an accident.
Several prior art inventions solve the problem by offering kits which retain the needle inside the medication administering system or allow the needle to be retracted back up inside the insertion apparatus and then discarded. Both Wanderer et al., U.S. Pat. No. 4,850,961 (1989) and Braginetz et al., U.S. Pat. No. 4,932,945 (June 1990) describe intravenous catheter insertion devices which include an insertion handle or housing that provide for retracting the needle inside the housing after the catheter has been inserted, thus allowing disposal of the entire insertion kit less the catheter. These devices are necessarily relatively bulky and therefore would be more difficult to manipulate relative to a simple insertion needle. They are also quite complex and would require a complete re-design of standard placement systems, resulting in a substantial increase in cost. Also, the user is obliged to perform more complex actions than with a simple insertion needle.
An invention by Jagger et al., U.S. Pat. No. 4,781,692 (1988) is different in that the insertion needle is withdrawn from the catheter but remains in a sealed housing and flexible tube to which the intravenous fluid lines are then attached. Such an approach, besides introducing increased complexity and increased costs also presents increased flow restriction with a sharp rigid needle inside a bulky housing which must remain attached to the patient's arm or other appendage often for extended time periods, resulting in increased discomfort at best and allowing a possibly dangerous situation to exist.
Ideally an intravenous needle guard should be entirely automatic in that the act of withdrawing the needle from the catheter causes the guard to become activated, therefore requiring no additional responsibilities or actions from the health care worker beyond those required by a standard insertion kit. In addition it should be quite simple and inexpensive, requiring the very minimum of insertion kit re-design. Such a device becomes possible if the guard were intended to enclose only the sharp tip instead of the entire needle.
One embodiment of an invention by Vaillancourt, U.S. Pat. No. 4,725,267 (1988) is a hypodermic needle tip guard, but it has no provision to be automatically activated when used in conjunction with an intravenous insertion kit and has no provision for resisting being pulled off the tip other than the slight pull offered by a small coil spring.
The same is true of a tip guard by Martin, U.S. Pat. No. 4,887,998 (1989), although it does additionally provide a small occluding ball to positively prevent penetration of the guard by the enclosed tip.
A hypodermic needle tip guard invented by Kulli, U.S. Pat. No. 4,929,241 (1990), likewise is not intended for automatic activation by intravenous insertion needle withdrawal and therefore has no provision for such, but it does have internal blades intended to grasp the needle tip when it becomes enclosed by the guard and therefore resists efforts to be pulled from the tip. Conceptually this approach offers a simple functional tip guard but practically speaking would fall short of an ideal guard if modified for IV needles.
Ideally such a guard would reside initially in available space inside the catheter hub until the needle is withdrawn, at which time it would close upon the tip. If the Kulli guard were miniaturized and placed inside the catheter hub the clamping force would not be sufficient. If placed over the needle outside the hub, complete re-design of the insertion kit would be required and usage would be made more difficult.
Tip guards of the Kulli type use the presence of the needle tip to oppose the clamping force. A substantial spring force is required for the clamping means to dig into the steel needle surface. The force is released when the tip enters the guard, so there would be significant additional drag on the needle as it is withdrawn from the catheter if this type of guard were used with an insertion kit.
A needle tip guard invented by Lemieux, U.S. Pat. No. 4,952,207 (1990) is specifically intended for usage with an I.V. insertion kit and it avoids high withdrawal drag by not needing high spring pressure to grasp the needle. It does, however, require that the end of the needle be modified by the addition of a slot on the side which allows the guard to capture the tip. In anticipation of a possible problem created by the slot, that of an unwanted flow of blood emanating from the slot and flowing between the inner surface of the catheter and the outer surface of the needle, the Lemieux specification proposes an additional thin membrane over the slot which would prevent leakage yet be flexible enough to still allow the guard to capture the tip. Such additional complexities are not desirable. The ideal needle tip guard from the standpoint of I.V. insertion kit manufacturers would be one that doesn't require any modification of existing needles.
In reviewing the prior art it becomes evident that one simple I.V. needle guard which satisfies all significant requirements from both the point of view of the users and the manufacturers does not yet exist.